SHBG hormone test – what is it done for?

Sex hormone binding globulin (SHBG) is a protein which is manufactured in liver. A small amount is also produced in brain, uterus, testes, and placenta. It binds and transports the sex hormones in blood. These include estradiol (estrogen) in women and testosterone and dihydrotestosterone in men. Bound to this protein, the above hormones remain in an inactive form.

The SHBG hormone test measures the concentration of this protein in blood. The amount of SHBG in blood varies with age, thyroid function and obesity. It is reduced in liver diseases and by androgens. Its levels are increased by estrogens and in hyperthyroidism.

In males, changes in SHBG level affect the level of testosterone in blood. In normal males, 40 to 60% of testosterone is bound to SHBG and the remaining is bound to albumin. About 1 to 2% of testosterone is unbound (free testosterone) and physiologically active. Although SHBG binds three hormones, the hormone that is critical in this test is testosterone. SHBG controls the amount of testosterone that is available to the tissues.

The uses of SHBG test in men

This test is done for assessment of testosterone levels. In males, it is the deficiency of testosterone and in females, an excess of testosterone leads to problems and calls for this investigation. This is usually done along with estimation of other hormones related to gonadal function.

A total testosterone level in the blood is also assessed. A lack of testosterone is related to infertility in males. It is also associated with a low sex drive, impotence or erectile dysfunction. A thorough clinical examination is essential before these tests are ordered. When the total testosterone levels are within normal limits but the above clinical features are present, then SHBG test is performed.

Estimation of blood levels of free testosterone, albumin protein and other sex hormones like prolactin, estradiol and luteinizing hormone (LH) can also be done to assess the hormonal balance of these patients. Low levels of free testosterone may be associated with decreased sex drive, loss of muscle mass, decreased bone mass and erectile dysfunction.

The role of SHBG test in women

The SHBG hormone test is a good hormone balance indicator.

A very small amount of testosterone is produced in females. The site of production of this hormone is in the ovaries and the adrenal glands. An excessive production of this male hormone can easily disrupt the hormonal equilibrium and result in multiple problems. These symptoms include hirsutism (male pattern of excessive growth of hair), amenorrhea (infrequent or absent menses), acne and infertility due to anovulation. These features are also seen in association with ‘polycystic ovarian syndrome (PCOS) in which there is excessive production of androgens.

What is the importance of abnormal level of SHBG?

A raised SHBG level results in increased binding of testosterone, thereby resulting in lesser hormone available to the tissues. On the contrary, if the SHBG level is low, more of testosterone is available for action. This helps in management of patients with abnormal level of hormonal balance.

Values of SHBG are raised in liver cirrhosis, hyperthyroidism, estrogen use (hormone replacement therapy and oral contraceptives) and hypogonadism (decreased sex hormones due to gonadal dysfunction).

It is reduced in obesity, polycystic ovarian syndrome, hypothyroidism, hirsutism, use of anabolic steroids, acne and cushing’s disease.

Other uses of SHBG test

SHBG concentrations are inversely related to body mass index and fasting insulin levels. There is an inhibitory effect of insulin on SHBG secretion. Scientific studies have found that SHBG levels could be a marker of insulin resistance. Also, an increased risk for noninsulin-dependent diabetes and overall mortality are associated with decreased SHBG levels in postmenopausal women.

SHBG levels are directly proportional to the concentration of blood cholesterol. Therefore, the measurement of SHBG in clinical practice can be a useful diagnostic tool for evaluating insulin resistance and risk of heart disease.

It’s all about health! I have academic background in drugs related Chemical Technology, as well as extensive professional experience in pharma and medical companies. My main area of interest is everyday life medicine. The goal of my articles is to give people informative answers to the questions that bother them, to dispel doubts and some common misbeliefs and also to inspire everyone to keep healthy lifestyle.